I can also confirm that gps have trouble getting a lock.
I was in some mountain area near sea for a few days and my device was sometime have trouble getting GPS lock.
Sometimes when starting car and standing still it takes a long time to get lock, other times working as expected. It happens few times after exiting tunnel to not be able to get lock.
When comparing phone and dudu7 on GPS test app phone almost always have double satellite number in view.
And when I can't get lock on dudu7 number in view is fewer than 15.
